1. Field of the Invention
The present invention relates to an imaging system.
Priority is claimed on Japanese Patent Application No. 2010-195974, filed Sep. 1, 2010, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
Conventionally, there is an imaging system that detects the spectrum of a sample arranged on a stage or the like (See Japanese Unexamined Patent Application, First Publication No. 2008-209627). FIG. 13 is a view illustrating a schematic configuration of a conventional imaging system disclosed in Japanese Unexamined Patent Application, First Publication No. 2008-209627. As shown in FIG. 13, in the conventional imaging system 10, a sample 1201 is arranged on a stage 1202, and light from a transmission light source 1203 is irradiated onto it via a condenser lens 1204. A driving device 1209 moves the stage 1202 in an X-axis direction and a Y-axis direction that intersect each other orthogonally. Light of a predetermined region transmitted through the sample 1201 passes through an image-forming optical system 1205 and forms an image on an imaging element 1207 and a spectrum detector 1208. At this time, some of the light from the sample 1201 that passed through the image-forming optical system 1205 is transmitted by an optical path diving device 1206 such as a half mirror and irradiated to an imaging element 1207, while some of the light is reflected and irradiated to the spectrum detector 1208.
The imaging element 1207 detects the light of a predetermined region of the sample 1201 that was irradiated via the image-forming optical system 1205, and obtains (captures) an image corresponding to the detected light. The spectrum detector 1208 detects the spectrum of the light of the predetermined region of the sample 1201 irradiated via the image-forming optical system 1205, and outputs a spectrum signal corresponding to the detected spectrum. The imaging element 1207 and the spectrum detector 1208 are arranged such that they detect light in the same region of the sample 1201, and the spectrum detector 1208 detects the spectrum in a predetermined region of the sample 1201 that is an imaging region of the imaging element 1207. The Z-axis shown in FIG. 13 is a direction orthogonal (perpendicular) to the plane formed by the X-axis direction and the Y-axis direction that the stage 1202 moves in.
One example of an imaging system is a virtual microscope. A virtual microscope is an imaging system wherein a stage is moved while an imaging element divides all or part of a sample into regions and captures images of them; the divided images (digital images) thereby captured are pasted together to form a single digital image (virtual slide) of the whole sample. With a virtual microscope, a virtual slide made by pasting together high-resolution divided images can be manipulated using, for example, a personal computer to change the magnification or observation position of the sample, which is being displayed on a monitor. Since the virtual slide created by a virtual microscope can be shared simultaneously with a plurality of locations by transmitting it via a network, use of virtual microscopes is proliferating in the field of telepathology. In telepathology, the color information of a sample observed by the virtual microscope must match that of the created virtual slide. Consequently there is a demand that a virtual microscope has high color reproduction characteristic of the sample image.
“Experimental evaluation of color image estimation method using multipoint spectrum measurements” by Tokyo Institute of Technology, Imaging Science and Engineering Laboratory, K. Ietomi et al., Proceedings of the 54th Spring Meeting, JSAP and Related Societies, 2007 Spring (which is hereinafter referred to as a Non-Patent Literature 1) discloses an example of a technology that corrects the image captured by the imaging element to enhance the color reproduction characteristic of the captured image (sample image). The technology for enhancing the color reproduction characteristic of a captured image disclosed in Non-Patent Literature 1 will be explained by using FIG. 14. FIG. 14 is a pattern diagram illustrating the technology for enhancing the color reproduction characteristic of a captured image disclosed in Non-Patent Literature 1. In FIG. 14, region 1301 is one where an imaging element detects light of a predetermined region of a sample that forms an image in a focal plane, and region 1302 is one which a spectrum detector detects the spectrum of the light in the focal plane.
Here, ‘focal plane’ is the irradiation area of the light in the plane where light from the sample forms an image. In the technology disclosed in Non-Patent Literature 1, an RGB camera and a multi-band camera are used as the imaging element and the spectrum detector. In the technology disclosed in Non-Patent Literature 1, the image captured by the imaging element (sample image) is corrected on the basis of information used in color-correction that is contained in a spectrum signal output from the spectrum detector (which is hereinafter referred to as ‘spectrum information’), thereby enhancing the color reproduction characteristic of the sample image.
Conceivably, if the technology disclosed in Non-Patent Literature 1 is applied in the imaging system disclosed in Japanese Unexamined Patent Application, First Publication No. 2008-209627, this would achieve an imaging system that obtains a sample image with enhanced color reproduction characteristic as demanded by a virtual microscope. Specifically, in the conventional imaging system 10 shown in FIG. 13, the imaging element 1207 corrects the captured image on the basis of spectrum information output from the spectrum detector 1208. This can enhance the color reproduction characteristic of the image of the sample 1201.
When the technology disclosed in Non-Patent Literature 1 is applied in the imaging system disclosed in Japanese Unexamined Patent Application, First Publication No. 2008-209627, the spectrum detector 1208 of the conventional imaging system 10 shown in FIG. 13 is used for enhancing the color reproduction characteristic of the sample image captured by the imaging element 1207. Therefore, to correct the color reproduction characteristic of the sample image at high resolution, a sufficient quantity of light must be made incident to the spectrum detector 1208.
However, in the conventional imaging system 10 shown in FIG. 13, the optical path-diving device 1206 divides light from the sample 1201 that passed through the image-forming optical system 1205, and light is then irradiated to the imaging element 1207 and the spectrum detector 1208. Therefore, only some of the light from the sample 1201 is irradiated to the imaging element 1207 and the spectrum detector 1208. Consequently, a sufficient quantity of light cannot reliably be made incident to the spectrum detector 1208, resulting in a reduction in the signal-to-noise ratio (SNR), which expresses the amount of noise in the spectrum signal output from the spectrum detector 1208. Depending on the region where the sample 1201 is being observed, the transmissivity of the light from the transmission light source 1203 decreases, and the signal output of the spectrum signal from the spectrum detector 1208 becomes so small that the signal component is buried in noise. Consequently, the SNR of the spectrum signal decreases even further.
When attempting to enhance the color reproduction characteristic of the sample image captured by the imaging element 1207 on the basis of the spectrum information output from the spectrum detector 1208 in this state, sufficient correction is impossible, and the color reproduction characteristic of the sample image cannot be enhanced. This is due to the low SNR of the spectrum signal output from the spectrum detector 1208.